##submission.abstract##
Background: Spinal anaesthesia with bupivacaine alone provides reliable intraoperative anaesthesia but limited postoperative analgesia. Intrathecal adjuvants such as clonidine and fentanyl have been used to prolong analgesia, each acting through distinct receptor mechanisms.1,4
Objectives: To compare block characteristics, sedation, duration of postoperative analgesia, and side effects between intrathecal clonidine and fentanyl as adjuvants to hyperbaric bupivacaine in lower limb orthopaedic surgery.
Methods: This was a prospective, randomised, double-blind study of 100 patients undergoing lower limb orthopaedic surgery under spinal anaesthesia, allocated to receive intrathecal bupivacaine 15 mg with either clonidine 50 mcg (Group C, n=50) or fentanyl 25 mcg (Group F, n=50). Onset and duration of sensory and motor block, sedation score, duration of effective analgesia, requirement for rescue analgesia, and side effects were recorded and compared.
Results: Duration of sensory block (268.4 ± 32.7 min vs 198.3 ± 26.4 min), motor block (224.7 ± 28.3 min vs 182.5 ± 24.1 min), and effective analgesia (342.6 ± 38.9 min vs 246.8 ± 31.5 min) were all significantly longer in the clonidine group than the fentanyl group (all p<0.001). Rescue analgesia was required in 18.0% of the clonidine group compared with 42.0% of the fentanyl group. Sedation scores were higher with clonidine, while pruritus was more common with fentanyl.
Conclusion: Intrathecal clonidine provides significantly longer postoperative analgesia than fentanyl when used as an adjuvant to hyperbaric bupivacaine for spinal anaesthesia in lower limb orthopaedic surgery, at the cost of greater sedation, while fentanyl is associated with a higher incidence of pruritus.